Filament support for tubular lamps



July 13, 1965 T. HEINLEIN 3,194,999

FILAMENT SUPPORT FOR TUBULAR LAMPS Filed 001;. 28, 1963 ITWVTWTOT-I Leon T. Heinlein by @25/7 His A t tovneg United States Patent Office Bdfidfihh Patented July 13, 1965 3,194,999 FILAMENT SUPPDRT FGR TUBULAR LAMPS Leon T. Heinlein, Euclid, Qhio, assignor to General Electric Company, a corporation of New York Filed Get. 28, 1963, Ser. No. 319,213 8 (Ilairns. (til. 313-271) This invention relates generally to electric incandescent lamps, and more particularly to tubular lamps having an axially extending coiled filament. Still more particularly, the invention relates to filament supports for lamps having coiled coil filaments, i.e., filaments formed by winding the filament wire to form a helical primary coil which is again helically coiled to form the secondary coil of the coiled coil filament.

In tubular lamps of the double ended type having an axially extending filament connected at its ends to lead-in conductors sealed through opposite ends of the envelope, it has been the practice to provide auxiliary support members at one or more locations on the filament intermediate its ends, to support the filament from the envelope walls and maintain it generally at the axis of the envelope. For a filament in the form of a simple helical coil, a widely used form of support comprises a Wire member having one end coiled around the exterior of several turns of the heli cal filament coil and extending therefrom, usually in the general form of a spiral, to be circumfcrentially engageable with the inner Wall of the envelope. However, such a support is not suitable for coiled coil filaments, particularly filaments of high wattage and therefore relatively large size. Previous attempts to provide a suitable support for coiled coil filament lamps have suifered from various disadvantages such as failure to firmly support the filament in the axis of the envelope, ditficulty in making the support and assembling it with the other lamp components, and electrical short circuiting of portions of the filaments in varying degrees, or requiring additions to the length of the filament thereby nullifying, to some degree, the desirable compactness of a coiled coil filament.

It is therefore an object of the invention to provide a support structure which will obviate the above-stated disadvantages to provide a support member of relatively simple design and ease of assembly and which will firmly support the coiled coil filament in the axis of the envelope.

Briefiy stated, and in accordance with one aspect of the invention, the coiled coil filament is interrupted or separated at a point intermediate its ends to define separate sections or segments, and the adjacent interrupted ends are joined by a support member comprising wire portions which are formed to conform to at least a portion of a turn of the secondary coiling of the filament and which are fitted as mandrels or cores in the interior of the primary coiling of respective interrupted adjacent ends of the coiled coil filament sections. Additional portions of the support member are formed to support the said mandrel wire portions from the inner wall of the lamp envelope.

Further features and advantages of the invention will appear from the following detailed description of species thereof, and from the rawing wherein:

PEG. 1 is a side elevation of a lamp having a filament support member in accordance with the invention;

' FIG. 2 is a section of the lamp taken along the line llll in FIG. 1;

FIG. 3 is a perspective view of the support member with portions of the filament segments attached thereto;

FlG. 4 is a perspective view of the support member alone and in slightly modified form;

FIG. 5 is a perspective view of a further modification of the support member;

FIG. 6 is a perspective view of still another modification of the support member;

FIG. 7 is an exploded perspective view of another modification of the support member;

FIG. 8 is a longitudinal section through the support of FIG. 7; and

FIG. 9 is an exploded perspective view of still another modified support member.

Referring to FIG. 1 of the drawing, the lamp illustrated therein comprises a tubular envelope 1 of vitreous material having compressed pinch seals 2 at its opposite ends through which extend lead-in conductors 3 having their inner ends connected to respective ends of a coiled coil filament 4 which extends axially of the envelope. The lamp may be of the so-called iodine cycle type wherein the filament 4 is of tungsten wire and the envelope 1 contains a quantity of iodine which functions as a regenerative getter to return to the filament 4 tungsten which is vaporized therefrom during operation of the lamp, as described and claimed in Patent 2,883,571, Fridrich and Wiley. The envelope 1 preferably also contains a filling of inert gas such as nitrogen, argon, krypton, or xenon, or mixtures thereof, at substantial pressure preferably exceeding atmospheric. Since the envelope of such a lamp attains elevated temperatures exceeding 250 C., it is preferably made of glass of relatively high melting point such as borosilicate or alumino-silicate or quartz glass. Each of the lead wires 3 includes an intermediate foil portion 5, preferably of molybdenum, which is hermetically sealed in the pinch seal 3, an outer portion 6, preferably of molybdenum, and an inner portion '7, preferably of tungsten and which is connected to the adjacent end of the filament 4 in any suitable manner.

In order to support the filament 4 in the axis of the envelope, auxiliary support means are provided, in this case a single support member at the midpoint of the filament. For this purpose, and in accordance with the invention, the filament 4 is interrupted or separated at its midpoint to define separate sections or segments 4a and 4b which are joined at their adjacent interrupted ends by a support member 8.

The support member 8 (and 8a in FIG. 4) comprises helically coiled wire portions 9, preferably of about one turn of a helix or less, of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of the coiled coil filament 4.and fitted as mandrels or cores in the primary coiling of respective interrupted adjacent ends of the filament sections 4a and 4b, as shown in FIG. 3.

As shown in FIGS. 3 and 4, the coil turn portions 9 of the support are formed as free end portions of spuds comprising also straight leg portions 10 which extend in overlapping relationship along the axis of the envelope 1, with the axis of said coil portion 9 also coincident with the envelope axis to thereby support the filament 4 in said envelope axis. The spuds 9-H] are suitably supported from the envelope Walls, in the case of the FIG. 3 support, by a wire member having one end 11 tightly coiled about the overlapping legs 16 to bind them together, and.

extending therefrom as a straight arm section 12 generally radially of the envelope 1, thence in a loop portion 13, in this case of one and one-half turns and of a size to be circumferentially engageable with the inner wall of the envelope. of the support member 3, the loop portion 13 preferably terminates in an offset leg portion 14 which is firmly alfixed to the envelope, preferably by sealing it in a depression formed by the residue 15 of exhaust tubing used in evacuating and gas filling the envelope. Actually, the

wire 'portion 11, 12, 13 is preformed with the helic-ally.

coiled portion 11, and the legs 10 of the pigtail spuds are inserted into coil 11 from opposite ends.

It will be evident that the engagement of the loop portion 13 of the support with the envelope wall need not be In order to fully stabilize the position completely about its circumference. It should be engageable around at least half the circumference of the wall, for example, three-fourths of the circumference as shown by the loop portion 13a in FIG. 4, or it may be formed angularly, of V shape for example, to engage the envelope wall at three or more points spaced around the circumference.

- It will also be evident that the helically coiled portions 90 of the support do in FIG. 6 may be formed at opposite ends of a single wire 16c instead of the separate wire legs 10 of FIGS. 1-4. Furthermore, the loop portion 13 (13a, 13d) of FIGS. 1-4, 7 and 8, may be omitted and the arm portion, as shownat 120 in FIG. 6, may be extended and embedded in the envelope wall or in the exhaust tip 15.

The support member 3b of FIG. 5 is formed of a single length of wire having each end formed as the helical coil turn portions 9b on the ends of axially extending leg portion 16b each terminating in the radially extending arm portions 12b joined by the loop portion 13b which has an offset leg portion 14b for sealing to the envelope wall.

The presently preferred modification shown in FIGS.

7 and 8 is similar to that shown in FIGS. 1-4 except that the leg portions 1nd and 110d of the pigt-ail spud mem bers are helically coiled. The relative sizes of the coiled portions 1nd, 11nd and 11d are such that they can be screwed together in overlapping relationship. Preferably, the sizes are such that the coil 16d screws onto (over) the coil lid, and the coil 119d screws onto (over) the coil 10d, as shown in FIG. 8. The helical turns 9d and 199d are of enlarged diameter and of a pitch to fit into the primary coiling of the filament segments 4a and 411, just like the coil turns 9 in FIGS. 13. In the course of screwing the coil 10d over the. coil 11d, the enlarged turn 9d will pass over and beyond the'arm portion 12d as shown in FIG. 8. In order to center the loop portion 13d of the support longitudinally of the envelope, the arm portion 12d maybe bent at an angle as shown in FIG. 8 to bring the loop 13d into a transverse plane midway between the coil turns 9d and 109d.

In FIG. 9, one of the pigtail spud members of FIG. 7 is eliminated by forming directly on the free end of the helix 11c, the helical turn lti9e which is proportioned to fit into the primary coiling of one of the filament segments 4b of FIG. 1, thereby constituting the helix 11c and turn 1tl9e a spud member. The helically coiled leg 198 of the spud 9e, we is proportioned to screw into the helix 110, the helical turn 9e being proportioned to fit into the primary coiling of the other filament segment 4a of FIG. 1. The helix lle, along with the intermeshed spud 10a, 9e, is supported from the envelope wall by the arm portion 12c and loop portion 132.

It will be apparent that the helical coil portions 9 of the support member, being fitted as mandrels in end portions of the primary coiling of the filament segments 4a and 4b, provide for a firm supporting of the filament in the envelope axis, and with short circuiting of a relatively small and definitely reproducible portion of the filament coil.

While specific embodiments of the invention have been described herein, it will be evident that still further modifications, additions or omissions of the supporting structure may be made within the spirit and scope of the invention .as defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric incandescent lamp comprising a tubular envelope containing an axially extending helically coiled coil filament, said filament being interrupted at a point intermediate its ends thereby defining separate filament segments, and a support member joining the interrupted adjacent ends of said filament segments and supporting them from the envelope Wall, said support member comprising helically coiled wi-re portions 'of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of said coiled coil filament, said helically coiled wire portions being fitted as mandrels in the primary coiling or respective interrupted adjacent ends of said filament sections, and means supporting said helically coiled wire portions from the inner wall of said envelope with their axes substantially coincident with the envelope axis.

2. in an electric incandescent lamp comprising a tubular envelope containing an' axially extending helically coiled coil filament, said filament being interrupted at a point intermediate its ends thereby defining separate filament segments, and a support member joining the interrupted adjacent ends of said filament segments and supportingthem from the envelope wall, said support member comprising helically coiled wire portions of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of said coiled coil filament, said helically coiled portions being spaced apart axially of the envelope and supported by an axially extending wire portion, said helically coiled wire portions being fitted as mandrels in the primary coiling of respective interrupted adjacent ends of said filament sections, and means engaging said axially extending wire portion and supporting said helically coiled wire portions from the wall of said envelope with their axes substantially coincident with the envelope axis.

3. A lamp as set forth in claim 2 wherein the lastnamed means is a wire portion including a loop of a size to be circumferentially engageable with the inner wall of said envelope around at least half its circumference.

4. In an electric incandescent lamp comprising a tubular envelope containing an axially extending helically coiled coil filament, said filament being interrupted at a point intermediate its ends thereby defining separate filament segments, and a support member joining the interrupted adjacent ends of said filament segments and supporting them from the envelope wall, said support member comprising a pair of wire spuds having overlapping leg portions extending substantially axially of said envelope and terminating at opposite free ends in helically coiled wire portions of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of said coiled coil filament, said helically coiled wire portions being fitted as mandrels in the primary coiling of respective interrupted adjacent ends of said filament sections, and a wire portion having an end binding said overlapping leg portions together and extending therefrom into supporting engagement with the inner wall of said envelope.

5. In an electric incandescent lamp comprising a tubular envelope containing an axially extending helically coiled coil filament, said filament being interrupted at a point intermediate its ends thereby defining separate filaent segments, and asupport member joining the interrupted adjacent ends of said filament segments and supporting them from the envelope wall, said support member comprising a pair of wire spuds having overlapping leg portions extending substantially axially of said envelope and terminating at opposite free ends in helically coiled wire portions of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of said coiled coil filamencsaid helically coiled wire portions being fitted as mandrels in the primary coiling ofrespective interrupted adjacent ends of said filament sections, and a wire portion having an end coiled around said overlapping leg portions and binding them together and extending therefrom to a loop portion of a size to be circumferentially engageable with the inner wall of said envelope around at least half its circumference.

6. A lamp as set forth in clairn'S wherein the loop portion of said support terminates in an offset leg portion which is sealed to the adjacent wall portion of said envelope.

7. In an electric incandescent lamp comprising a tubular envelope containing an axially extending helically coiled coil filament, said filament being interrupted at a point intermediate its ends thereby defining separate filament segments, and a support member joining the interrupted adjacent ends of said filament segments and supporting them from the envelope wall, said support member comprising spud members including helically coiled wire portions of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of the filament and fitted as mandrels in the primary coiling of respective interrupted adjacent ends of said filament sections, said spud members further including respective helical leg portions extending axially of the envelope and joined together in overlapping screw threaded interengagement, and means engaging at least one of said helical leg portions and supporting said spud members from the Wall of said envelope with the axes of said helically coiled wire portions substantially coincident with the envelope axis.

8. In a lamp as set forth in claim 7, the last-named. means including another helical portion which is joined in screw thread interengagemcnt with at least one of said helical leg portions.

No references cited.

DAVID J. GALVIN, Primary Examiner. 

5. IN AN ELECTRIC INCANDESCENT LAMP COMPRISING A TUBULAR ENVELOPE CONTAINING AN AXIALLY EXTENDING HELICALLY COILED COIL FILAMENT, SAID FILAMENT BEING INTERRUPTED AT A POINT INTERMEDIATE ITS ENDS THEREBY DEFINING SEPARATE FILAMENT SEGMENTS, AND A SUPPORT MEMBER JOINING THE INTERRUPTED ADJACENT ENDS OF SAID FILAMENT SEGMENTS AND SUPPORTING THEM FROM THE ENVELOPE WALL, SAID SUPPORT MEMBER COMPRISING A PAIR OF WIRE SPUDS HAVING OVERLAPPING LEG PORTIONS EXTENDING SUBSTANTIALLY AXIALLY OF SAID ENVELOPE AND TERMINATING AT OPPOSITE FREE ENDS IN HELICALLY COILED WIRE PORTIONS OF A COIL DIAMETER AND PITCH CORRESPONDING SUBSTANTIALLY TO THE DIAMETER AND PITCH OF THE SECONDARY COILING OF SAID COILED COIL FILAMENT, SAID HELI- 